Leaks

Signs of a Hidden Water Leak

Common warning signs that a leak may be developing where you can't see it.

Why hidden leaks matter

A hidden leak can develop where you can't easily see it, behind a wall, under a floor, or at a fitting. Left alone, even a slow drip can damage materials and raise your water bill. Catching signs early and asking for an assessment helps you understand what's happening.

Signs to watch for

  • Damp stains on ceilings, walls, cabinets, or floors.
  • The sound of water running when no fixtures are on.
  • A water bill that rises without a change in your usage.
  • Musty odors or visible mold near plumbing.
  • Warm or buckled flooring near a hot-water line.

What to do next

Note when you first noticed the sign, where it is, and anything that changed recently. If it's safe to do so, take a photo. Share these details when you request service. See our guide on what to send a plumber for a full checklist.

This guide is informational and doesn't replace a professional assessment of your situation. For your safety, don't enter flooded areas with electrical equipment or touch energized appliances.

Need help with a plumbing problem?

Call us or send a service request. We're based in Oakland and serve the entire Bay Area, 24/7.